Science Serving Maryland's Coasts

Cherie Peranteau, Richard Stockton College

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Estuarine Bacterioplankton Metabolism and Diversity Across a Seasonal Oxygen Gradient


The Chesapeake Bay contains chemical and biological gradients that influence bacterioplankton communities. Heterotrophic bacteria in the spring create anoxia and establish a seasonal oxygen gradient lasting until fall. Bacterioplankton communities have not yet been studied across a seasonal oxygen gradient. Community composition and cell abundance was examined in June and July, production in July and August, and respiration in August. The composition of bacterioplankton communities was characterized with denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA. As anoxia set in, community composition shifted only slightly in both surface and bottom waters. Similarly, community composition varied only slightly between oxic and anoxic waters. Bacterial abundance revealed similar trends in hypoxic and anoxic waters, but as anoxia set in an unusual sheathed cell became numerically dominant in anoxic and hypoxic waters. Bacterial production also exhibited similar trends across the oxygen gradient. Respiration was highest at the top of the gradient and decreased in the middle, but then increased near the bottom of the oxycline in extremely hypoxic waters. This implicates that the seasonal oxygen gradient influences the composition and activity of bacterioplankton communities.

The results of this work were presented at the American Society of Limnology and Oceanography (ASLO) 2005 Aquatic Sciences meeting. Download the poster (pdf, ~230kb).